Use golangci-lint fmt to format code (#163)

Use `golangci-lint fmt` to format code, upgrading `.golangci.yml` to v2 and mirroring the linter configuration used by https://github.com/go-gitea/gitea. `gci` now handles import ordering into standard, project-local, blank, and default groups.

Mirrors https://github.com/go-gitea/gitea/pull/37194.

Changes:
- Upgrade `.golangci.yml` to v2 format with the same linter set as gitea (minus `prealloc`, `unparam`, `testifylint`, `nilnil` which produced too many pre-existing issues)
- Add path-based exclusions (`bodyclose`, `gosec` in tests; `gosec:G115`/`G117` globally)
- Run lint via `make lint-go` in CI instead of `golangci/golangci-lint-action`, matching the pattern used by other Gitea repos
- Apply safe auto-fixes (`modernize`, `perfsprint`, `usetesting`, etc.)
- Add explanations to existing `//nolint` directives
- Remove dead code (unused `newRemoteReusableWorkflow` and `networkName`), duplicate imports, and shadowed `max` builtins
- Replace deprecated `docker/distribution/reference` with `distribution/reference`
- Fix `Deprecated:` comment casing and simplify nil/len checks

---
This PR was written with the help of Claude Opus 4.7

Reviewed-on: https://gitea.com/gitea/act/pulls/163
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-committed-by: silverwind <me@silverwind.io>

pkg/container/docker_socket.go

@@ -43,8 +43,8 @@ func socketLocation() (string, bool) {
 // indicating that the `daemonPath` is a Docker host URI. If it doesn't, or if the "://" delimiter
 // is not found in the `daemonPath`, the function returns false.
 func isDockerHostURI(daemonPath string) bool {
-	if protoIndex := strings.Index(daemonPath, "://"); protoIndex != -1 {
-		scheme := daemonPath[:protoIndex]
+	if before, _, ok := strings.Cut(daemonPath, "://"); ok {
+		scheme := before
 		if strings.IndexFunc(scheme, func(r rune) bool {
 			return (r < 'a' || r > 'z') && (r < 'A' || r > 'Z')
 		}) == -1 {